1. Field of the Invention
The present invention relates, in general, to a method for rapid robotic handling of small articles removed from molds. More specifically, the present invention pertains to such a method which is particularly well suited for removing the articles from a molding machine having molds in which they are molded, and thereafter carrying the articles within a very short period of time away from the molds and depositing the articles for further processing in a high speed, automated production system.
2. Description of the Prior Art
Recently, attention has been directed by industry toward economically forming large quantities of high-quality contact lenses in a precisely operating, high-speed automated molding system. In such a lens molding system, each lens is formed by sandwiching a monomer in an interspace which is present between front and back mold sections, normally identified as, respectively, front and base or back curves. The monomer is polymerized to form a contact lens, which is then removed from the mold sections, further treated and then packaged for consumer use.
The mold sections used in the above-mentioned process may themselves be formed through the intermediary of injection molding or compression molding processes. These mold sections may be made from the family of materials consisting of thermoplastics; for example, preferably such as polystyrene, which has been determined to constitute an excellent material for making these mold sections. Polystyrene does not chemically react with the hydrophilic material normally employed to make the contact lenses; for instance, such as hydroxy ethylene methacrylate (HEMA). Therefore, it is possible to form very high quality contact lenses of that type of material in polystyrene molds. In addition, polystyrene is widely available in industry and commerce and, as a result, is relatively inexpensive. Because of the ease and low cost with which polystyrene mold sections may be produced and then employed to mold contact lenses, each pair of complementary front and base curve polystyrene mold sections is typically used only a single time in order to mold only one contact lens, and may then be discarded or recycled for other uses.
In the above-discussed automated contact lens production system, it is desirable to eliminate or to minimize any exposure to oxygen of the hydrophilic monomer used for the manufacture of the contact lenses. Correspondingly, it is desirable to eliminate or minimize the exposure of the lens mold sections to oxygen. Therefore, when the polystyrene mold sections are formed and then used for the purpose of making contact lenses in the above-discussed manner, it is desirable to rapidly transfer these mold sections from the mold in which they are made to a low oxygen (preferably nitrogen) environment. It has been difficult to achieve the desired transfer speed with conventional robot assemblies or controls because presently available robots do not move with adequate rapidity and precisely enough to enter into, and exit from, the molding apparatus at the desired rate of speed in effectuating the removal of the molded articles. In particular, if these robots are operated at the necessary rate of speed, they tend to waffle and shake or vibrate undesirably as they come to a sudden stop, and the movements of the robot are resultingly not sufficiently precise. On the other hand, if the robots are slowed down so as to be able to move more precisely, the robots no longer possess the desired speed to facilitate the contact lens mass-producing process.
Moreover, in the above-mentioned automated contact lens production system, the contact lens mold sections may not be fully solidified when they are ejected or removed from the mold in which they are formed. It is, therefore, important that any robot or apparatus which is used to carry the contact lens-forming mold sections away from that mold will not interfere so as to adversely affect the desired optical qualities of the contact lens mold sections. In particular, it is important that any such robot or apparatus be capable of absorbing the kinetic energy of the lens mold sections as they are being transferred to such transporting robot or apparatus without deleteriously altering the shape, form or dimensions of the lens mold sections. The robot and mold transfer method employed must, likewise, be able to transport the lens mold sections in a manner that permits those lens mold sections to cool and completely harden in a desired manner.
In addition, in order to maximize the optical quality of the contact lenses, it is preferred that the optical surfaces of the front and base curve polystyrene mold sections; that is, the surfaces of those mold sections which touch or lie against the hydrophilic monomer as the lens preform is being molded, not be engaged or contacted by any mechanical handling equipment while the mold sections are being transported by and positioned in the lens molding system.
In order to achieve the foregoing kind of transport system, pursuant to the disclosure of copending U.S. patent application Ser. No. 08/258,267 now U.S. Pat. No. 5,681,138, there is described an apparatus for removing and transporting ophthalmic or contact lens mold sections from a mold, and which generally comprises first, second and third assemblies. The first assembly removes the lens mold sections from the mold and transports the lens mold sections to a first location, the second assembly receives the lens mold sections from the first assembly and transports the lens mold sections to a second location, and the third assembly receives the lens mold sections from the second assembly and transports the lens mold sections to a third location. Preferably, the first assembly comprises a hand including vacuum structure to receive the lens mold sections from the mold and to releasably hold the lens mold sections, and a support subassembly connected to the hand to support the hand and to move the hand between the mold and the first location.
The second assembly preferably includes a support frame, a platform to receive the lens mold sections from the first assembly and supported by the support frame for movement between the first and second locations, and moving means for moving the platform along the support frame and between these first and second locations.
The preferred design of the third assembly includes a transport subassembly and a support column. The transport subassembly receives the lens mold sections from the second assembly, releasably holds those lens mold sections, and carries the lens mold sections to the third location; and the support column supports the transport subassembly for movement between the second and third locations.
In an effort designed to simplify and provide further improvements on the foregoing transport apparatus, alternative embodiments have been developed more recently, as disclosed in copending U.S. patent application Ser. No. 08/431,884 now U.S. Pat. No. 5,540,543, which discloses an apparatus for removing and transporting articles, such as ophthalmic contact lens mold sections, or primary contact lens packaging elements, such as the base members of blister packages, from a mold. The apparatus, in one embodiment thereof, which is employed in the manufacture of lens mold base curves, includes first, second, and third assemblies; the first of which removes the articles from the molding station at a first location and transports them to a second location; the second assembly receives the articles from the first assembly and transports them to a third location, and the third assembly receives the articles from the second assembly and transports them to a fourth location.
A second embodiment of the apparatus which is used in the forming of lens mold front curves additionally includes a flipper assembly disposed between the first and third assemblies, which flipper assembly receives the articles from the first assembly and inverts them before depositing them onto the third assembly. This second embodiment is useful in conjunction with molded articles which are transported to the flipper assembly in an inverted position.
A third embodiment, which produces primary packaging components, such as the base members of blister packages for housing the contact lenses, includes second and third assemblies which further include means for altering the relative spacing between the articles while the articles are being transported.
Although the foregoing embodiments and operative versions of the apparatus, as elucidated in the aforementioned copending U.S. patent applications, are employable in providing the molded components constituting mold sections for forming contact lenses, and also primary package elements for contact lenses, such as the contact lens-receiving base members of blister packages, there are problems associated with vibration, speed and rejection of molded components overly exposed to oxygen. The numerous operating and transfer assemblies and stations which are required for transporting the molded components at high rates of speed from the molding installation in which they are formed to their ultimate depositions onto pallets for further treatment, such as in a low oxygen or nitrogen atmosphere, are of considerable complexity, subject to waffling and vibration and rendering the efficacy of producing acceptable articles difficult to maintain as a result of the multiplicity of operative apparatus components, and transfer and transport paths employed in the various apparatus embodiments. For example, numerous programmable logic controllers (PLCs) used to individually control various sections of the assemblies and stations prevent increasing operating speeds and reducing oxygen exposure time. This is due, for example, to the time needed for the PLCs to communicate with each other or with other PLCs of downstream or upstream assemblies.